1. Field of the Invention
This invention relates to multipoint systems for interconnecting work stations and, more particularly, to a multipoint connection system capable of operating in the time-division multiplex mode.
2. Prior Art
In-plant communication systems generally require that each of the work stations associated with the system be capable of handling voice, text, image and data processing applications and that all work stations be coupled to a central switching and data processing unit. Because the coupling of the central unit to the communication links accounts for a substantial portion of the overall cost of the system, it is desirable that a given line be shared by several work stations. For the purposes of voice (i.e. telephone) applications, each station requires an independent channel which can be economically provided through the use of the time-division multiplexing technique. For other applications, the stations can be made to share a common channel by means of a particular access protocol.
Loop connection systems have two main advantages, namely, their compatibility with the time-division multiplexing technique and the efficiency of the access protocols. However, such systems are somewhat deficient in the areas of reliability and availability. Multipoint connection systems, on the other hand, are reliable and make it easy to couple an additional station to the system without having to interrupt the operation of the other stations, but are particularly unsuited to operation in the time-division multiplex mode, as will be shown in detail hereafter with reference to FIGS. 2A and 2B.